我们如何存储到NSDictionary中？ NSDictionary和NSMutableDictionary有什么区别？ [英] How can we store into an NSDictionary? What is the difference between NSDictionary and NSMutableDictionary?

问题描述

我正在开发一个应用程序，我想在其中使用 NSDictionary 。任何人都可以给我发一个示例代码，解释如何使用 NSDictionary 来存储数据的完美示例吗？

I am developing an application in which I want to use an NSDictionary. Can anyone please send me a sample code explaining the procedure how to use an NSDictionary to store Data with a perfect example?

推荐答案

NSDictionary 和 NSMutableDictionary 文档可能是你最好的选择。他们甚至有一些关于如何做各种事情的很好的例子，比如......

The NSDictionary and NSMutableDictionary docs are probably your best bet. They even have some great examples on how to do various things, like...

...创建一个NSDictionary

NSArray *keys = [NSArray arrayWithObjects:@"key1", @"key2", nil];
NSArray *objects = [NSArray arrayWithObjects:@"value1", @"value2", nil];
NSDictionary *dictionary = [NSDictionary dictionaryWithObjects:objects 
                                                       forKeys:keys];

...迭代它

for (id key in dictionary) {
    NSLog(@"key: %@, value: %@", key, [dictionary objectForKey:key]);
}

...让它变得可变

NSMutableDictionary *mutableDict = [dictionary mutableCopy];

注意：2010年之前的历史版本：[[dictionary mutableCopy] autorelease]

...并改变它

[mutableDict setObject:@"value3" forKey:@"key3"];

...然后将其存储到文件中

[mutableDict writeToFile:@"path/to/file" atomically:YES];

...并再次阅读

NSMutableDictionary *anotherDict = [NSMutableDictionary dictionaryWithContentsOfFile:@"path/to/file"];

...读取值

NSString *x = [anotherDict objectForKey:@"key1"];

...检查密钥是否存在

if ( [anotherDict objectForKey:@"key999"] == nil ) NSLog(@"that key is not there");

...使用可怕的未来语法

从2014年开始你可以输入dict [@key]而不是[dict objectForKey：@key]

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